Since 2009 both have had a "book-to- bill ratio" sitting above one and Damien Lasou, senior vice president aerospace and defense at Capgemini Consulting, said that couldn't continue.
"If you sell more than you deliver then there is a promise that that is not being kept. They [both] have had to increase the number of deliveries significantly," he said by phone Monday.
Until the end of May this year Airbus had only received 73 orders while Boeing had notched up 205 requests for a new plane. By comparison, over the course of 2014 Airbus received 1456 orders while Boeing took 1432.
Boeing's website claims an order backlog of 5744, while at a press conference in January Airbus claimed a backlog of 6874 planes.
Lasou said global demand for large commercial planes is set to remain robust and that he expected both firms to now focus on speedier delivery.